Use Of Thermal-Hydraulic Computer Program To Help Predict What Happens In The Wellbore During A Subcool Event In Which Live Steam Enters A Production Liner

Abstract

The author recently attended the 2015 CHOA/SPE conference "Slugging It Out". There was a very good presentation made by Devon outlining risk analysis for jetting events in the liner. The root cause was identified as a subcool event in the wellbore. A subcool event is known to lead to sand entrainment in production, which eventually affects wellbore and then wellhead integrity. The presentation will outline what happens when live steam enters a segment of the wellbore and the predicted response. The analysis was conducted with WAHA, which is specialty thermal hydraulics program. The program differs from most SAGD well calculation packages that are based on steady state pressure drops. The program uses a 6 equation formulation. Liners are affected by thermal expansion due to heating which can have different effects depending on the degree and timing of collapse of the formation around the pipe. The burst and collapse strength of the pipe can be considerably changed. Slots are engineered to keep sand production out. Above the slots the sand grains form a matrix of interconnected grains that bridge across the slot. This is normally determined from a particles size distribution. Understanding how subcool leads to jetting is critical to determining the root cause of significant liner and tubing damage, expensive workovers and potentially loss of well integrity. Appropriate response depends on understanding the cause.